1. Field of the Invention
The present invention is directed to a video processing system having a filter circuit with a spatial-frequency high-pass characteristic, of the type suitable for use in an x-ray diagnostics installation for displaying an x-ray image, with enhanced fine contrast.
2. Description of the Prior Act
A problem in the video portrayal of x-ray images is that video images of this type have a very high dynamic (i.e., range of signal processing capability), because a relatively dart heart shadow must be transmitted and displayed as well as the extremely bright lung area. The physician, however, is hindered in interpreting the image in a thorax examination due to this extremely high dynamic, i.e. excessively bright lung fields.
A video installation of this type is described in German OS 34 17 386, which has a filter circuit having a variable high-pass filter characteristic connected to a control circuit which controls the filter circuit so that the full filter effect is employed in the presence of large signals, and substantially no high-pass filtering takes place in image regions having small signals. An optimum detail enhancement in all amplitude ranges, however, is not achieved in this known system.